Use sigprocmask rather than sigblock/sigsetmask.

No effect right now, because sigprocmask on LP32 also only touches
the non-RT signals, but this makes it easier to switch to __rt_sigprocmask.

Bug: http://b/72460436
Test: ran tests
Change-Id: I693f0ea36701e9ab5d10e6aefb26387ba45a6064
diff --git a/libc/arch-arm/bionic/setjmp.S b/libc/arch-arm/bionic/setjmp.S
index b814124..c10bd3e 100644
--- a/libc/arch-arm/bionic/setjmp.S
+++ b/libc/arch-arm/bionic/setjmp.S
@@ -218,8 +218,10 @@
   beq 1f
 
   // Restore the signal mask.
-  ldr r0, [r0, #(_JB_SIGMASK * 4)]
-  bl sigsetmask
+  mov r2, #0
+  add r1, r0, #(_JB_SIGMASK * 4)
+  mov r0, #2 // SIG_SETMASK
+  bl sigprocmask
 
 1:
   ldmfd sp!, {r0, r1, lr}